Shrinking my amp - Ohms issue?

[mr_sooty]

I've been thinking some more about my amp situation. Actually, it's just about all I think about.

I have the Classic 50 back, and played it at church on Sunday. Two services plus a practise for a conference we have coming up. Carrying the 61lb bohemith up the stairs of the MFC, along with my 2 guitars and pedalboard, I was thinking: this is SO not worth it, I'm getting a POD. But once we started playing, I changed my mind. It was SO good to have it back. I sounded like me again.

I was thinking, instead of getting a new amp, maybe I could build a new cabinet for mine and turn it into a 210. But I was wondering about Ohms.

The PV runs stock on 16ohms, and has an 8ohm and 16ohm speaker output. But I'm running the PV on 'half power', with 2 EL84's instead of 4. I like this better because I can crank it for power tube breakup if I want, it just seems like a good wattagem, just the right amount of headroom. I want to keep this set up. But I was advised that when I do this, I should plug the speaker cab into the 8ohm socket, because I have effectively halved it's capacity.

No if I take out 2 16ohm speakers (the speakers are all 16 ohms I believe, two series pairs in parallel with each other), I am left with 2 16 ohm speakers. Am I right in thinking that this will make 8ohms if run in series.

Can you run 2 speakers in parallel? Will this make 16 ohms ish? If I have to run them in series at 8ohms, will my amp be able to handle this load even running at half power? I'm concerned that if the speaker load is 8ohms, and I'm running my amp on half power, that I should be plugging the speakers into a 4 ohm socket, which the PV doesn't have.

Advice?

[sgt mukuzi]

hmmm not super sure about this but its as good as a bump
you can wire the 16 ohm speakers to 8 ohm or 32 ohm

if you run the amp with two less power tubes, your getting 25 watts (guessing...)

why dont you run one speaker at 16 ohms ( 8 ohms)

if your speaker is a 30 watter it should be ok on its own.

try a 1X12 cab at 16 ohms using the 8 ohm out put with 2 X el84

[AmpShop]

You've got the math for series and parallel backwards

If the idea is to halve the output impedance of the amp with respect to the speaker load, I'd suggest wiring two of the speakers in series to give you 32 ohm and connect that to the amp's 16 ohm output.

[bender]

Hey Cam, I have that partially completed cab if you want it. It's big enough for a single 12" speaker and just needs to be covered. Should fit the Peavey easy. Let me know if you're interested.

[Ears]

You've got the math for series and parallel backwards

If the idea is to halve the output impedance of the amp with respect to the speaker load, I'd suggest wiring two of the speakers in series to give you 32 ohm and connect that to the amp's 16 ohm output.

Geez sometimes these supposedly simple ratios get me really confused and I have to go get pencil and paper, but doesn't doubling the expected 16ohm load to 32 ohms by rewiring the spkrs have same effect as plugging the current 16 ohm load into the 8ohm socket?

[mr_sooty]

Hey Cam, I have that partially completed cab if you want it. It's big enough for a single 12" speaker and just needs to be covered. Should fit the Peavey easy. Let me know if you're interested.

You reckon? The PV is pretty wide. (checked - 608mm). I don't want a 112. I want 2x10's. But if it was wide enough I could just change the baffle.

If the idea is to halve the output impedance of the amp with respect to the speaker load, I'd suggest wiring two of the speakers in series to give you 32 ohm and connect that to the amp's 16 ohm output.

This seems to make sense. I've never heard of anyone using a 32ohm speaker load in an amp before though. Clearly I still haven't quite got my head around how ohms work.

Geez sometimes these supposedly simple ratios get me really confused and I have to go get pencil and paper, but doesn't doubling the expected 16ohm load to 32 ohms by rewiring the spkrs have same effect as plugging the current 16 ohm load into the 8ohm socket?

Pretty sure that's exactly what CAB was getting at.

[Ears]

Yeah ok, so if you wish to remove two speakers (I wasn't quite clear on that) and run only the remaining two at half power then I'm +1 with CAB.
But you can run all four the way you were originally advised.
Rule is (when spkrs are all same impedance) a series pair doubles the nominal value, and parallell connection halves it.

[mr_sooty]

Yeah ok, so if you wish to remove two speakers (I wasn't quite clear on that) and run only the remaining two at half power then I'm +1 with CAB.
But you can run all four the way you were originally advised.
Rule is (when spkrs are all same impedance) a series pair doubles the nominal value, and parallell connection halves it.

So all I gotta do is figure out which two are in series, unplug the other two, and I'd be able to hear what this is gonna sound like.

[Ears]

I think that'll be right.

[stark]

I've been thinking some more about my amp situation. Actually, it's just about all I think about.

LOL. I know exctly how you feel. It's easy to say to yourself "plenty of time - no hurry", but it ain't over till it's over. In fact it's never really over cos once you have one amp finished, finalised, and sorted, you start thinkin about another one.